On x86-64 branch servers the physics has been proven to be less reliable. These issues especially affect trains and tracks in all sorts of variants. Yes prop_static and brush tracks too. Even the best adjusted slider track combos will derail after a short ride, even at slow speeds. This might also apply to your trackback, not matter if they used as props or as prop_static.
For more details please see my report in the GMod repository:
On x86-64 branch servers the physics has been proven to be less reliable. These issues especially affect trains and tracks in all sorts of variants. Yes prop_static and brush tracks too. Even the best adjusted slider track combos will derail after a short ride, even at slow speeds. This might also apply to your trackback, not matter if they used as props or as prop_static.
For more details please see my report in the GMod repository:
Facepunch/garrysmod-issues#5968 - Unstable collision detection in physics on x86-64 branch